What can I do to fix a concrete slab slanted toward a garage?

A house I might but has a water drainage problem. The back of the garage has a concrete patio that is 1 foot below the lawn level. There are sidewalk type chunks of concrete up against the garage which are causing the problem the rest is an entire piece which is level. The concrete is about 1" below the siding for the garage. Near the corner of the garage there is a gutter that needs to be redirected but isn't a big problem. Can I do something or should I have a professional do this?